Archive for March 12th, 2011

WELCOME TO THE KREWE OF ACCRETIONARY WEDGE #32
It’s carnival time in the south and since the Accretionary Wedge is suppose to be a carnival of blogs and information I feel it is only fitting that we should have a parade of favorite geologic pictures to post. I’ve posted them in the order in which they were received.Thank you all for participating and making it such a wonderful parade.

Dana had a hard time picking on a favorite photo, so instead she picked a favorite geologic place to go to. Can’t you imaging yourself going there for some peace and quiet? Isn’t it a fantastic place to visit?

Here’s a little of what she wrote: ……. we’ll do this. We’ll cut to the chase and play a favorite – a favorite place, one of my favorite places in the world. We’ll take a trek through the desert and come upon an oasis.

Down around Camp Verde in Arizona, you’ll come across a picture-perfect karst terrain. The old beds of lake-deposited limestone lay flat, dry and hot under the sun, carved into gullies and hills by wetter times. In some places, sinkholes pit the scenery. They’re lovely examples of the power of water and gravity together to sculpt the scenery.

Camp Verde got its name because a river runs through it, causing a line of green to conga through the hot, scrubby hills. It was enough of a shock that explorers named it the Verde River, because it was very nearly the only green thing they’d seen for absolute miles.

You will have to go to her blog to read more about this delightful place.

The old Sinagua canal

She ended with and I agree:Now that you’ve had a nice rest at the water’s edge, on with the parade!

He writes:So here’s one of my favorite pictures – Haleakala crater. Technically, this isn’t the actual crater, it’s the eroded summit, widened by erosion. The smaller hills are cinder cones that erupted after most of the shield volcano was eroded away.

Here’s the float from Jessica at Magma Cum Laude with this beautiful picture. She writes:One of my favorite geologic photos is plenty colorful – and it’s also from my first field course, a month-long tour of the Colorado Plateau. The contrast between the sand and sky at Coral Pink Sand Dunes State Park in Utah is truly striking, and it was one of my favorite stops on the trip – because it’s also an excellent place for a game of frisbee!

From Evelyn we have a first time entry for the AW. Welcome aboard Evelyn!!! Here’s her float from Georneys

She writes:One of my favorite geology pictures (I have several- so difficult to chose!) is a picture of my favorite campsite ever. The picture below shows a makeshift campsite just off a road in northern Oman. The beautiful mountain in the background is Jebel Misht, one of several exotic limestones in the middle of the Samail Ophiolite. I was lucky enough to spend a few nights at this campsite in 2009 and 2010 as part of my PhD thesis fieldwork. One of my field sites, located near the small village of Al-Bana and close to the Misht campsite, has been named “Jebel Misht Travertine” by my research group.

Jebel Misht is a popular climbing destination. Making your way up the tall southeast cliff is not an easy task. When a French team of climbers accomplished the first successful ascent of Jebel Misht in 1979, the Sultan of Oman arranged to have the climbers picked up by helicopter from the top of the mountain and whisked off to the palace for a celebration. Jebel Misht means “Comb Mountain” in Arabic. Indeed, the mountain’s majestic cliff resembles a gigantic comb resting peacefully amidst the seafloor rocks of the ophiolite.

He writes.…. While it’s not my favorite, it’s definitely a favorite, more by virtue of the geology it shows than the aesthetic qualities of the image:
That is an outcrop of the French Thrust, one of many imbricate thrust faults exposed in Sun River Canyon, Montana, just west of Augusta. The light colored rock at right is limestone and dolostone of Mississippian age, and the dark rock at the lower left is shale of Cretaceous age (deposited in the Western Interior Seaway). Beyond that, to the very far left, you can see some lighter-colored, poorly-sorted material. That’s Pleistocene glacial till, and both the shale and the till are capped by a sloping layer of colluvium, tumbling down from higher elevations. The contact between the shale and the dolostone is a thrust fault. Half a mile downstream there is another. Half a mile upstream there is another. There are a lot of them exposed in Sun River Canyon, and the Canyon cuts across strike of all of them. Note the syncline in the Mississippian carbonates, and the differential weathering of the carbonate (tough, proud) as compared to the shale (weak, depressed). Here’s an annotated version of the photo:The Sun River Canyon is an unparalleled location in my experience for gorgeous scenery, great weather, a minimum of people, a healthy population of great gray owls, and exceptional exposures of an imbricate stack of thrust sheets. Check out this old post I put up at Pathological Geomorphology for more details about the area.

It’s always hard to pick a favorite geology picture, but this wintery Crater Lake panorama tops my list right now. Crater Lake is one of my favorite places, and it was exciting to visit in the winter! The perfect mirroring effect was particularly stunning. In person, the sky and water were the same color, making the caldera look like an arch in the sky.

Gareth’s float at Science 2.0 is very interesting to see because it has a volcanic bomb in it. This is one of the few bombs I care to see. In fact I wouldn’t ming going to Satorini to check it out for myself.

Despite my relatively short career as a geologist, it was a hard choice. There was a spectacular fault outcrop in Arkitsa, Greece; some impossible-looking resistant beds sticking straight out of the forest near Benés in the Catalan Pyrenees; and the classic ‘ripples on a vertical surface‘ to illustrate tectonic forces, also in the Catalan Pyrenees. However, I decided on this photo in the end, mainly because now I am a proper volcanologist I felt I should choose a volcano-related picture.

The photo is from Santorini, and shows a volcanic bomb. The layer it has impacted into is about 2m thick. While this is far from the largest bomb on the island, the way it is exposed here really does emphasise the power released when a volcano decides to blow.

The Eagle Mts. (an Oligocene caldera) were the site of my originally-intended Master’s Thesis work, during the summer of 1978. The photo here was taken from the East Mill area, where we camped, for several weeks, while we mapped the southeastern portion of the mountains. In the near foreground is a portion of Wyche Ridge, composed of Cretaceous sedimentary rocks, forming part of the margin of the caldera.
Please go to his blog to read the rest of what he has to say about this area.

This what John has to say about his picture: Last summer I drove out to Bozeman, Wyoming for a GIS conference and took a rather circuitous route both outward from and back into Vermont. We decided to camp at Buffalo Bill State Park along the reservoir and then return to Cody after setting everything up. On our way back into Cody, just before the famous rodeo stadium, the setting sun illuminated this fantastic angular unconformity exposed in the Shoshone River. Based solely on the descriptions found in Torres and Gingerich (1983) I think the lower reddish unit is the Eocene Wildwood Formation overlain by the volcaniclastic Aycross Formation. I haven’t done any work at all, so this is solely based on reading geologic descriptions, hope I’m close.

View Angular Unconformity in a larger mapAnd here is a closer view of the contact; again I ‘think’ my interpretation is correct but please advise if I’m off base here!

Ian at Hypo Theses has another fascinating picture of distant shores for his float.

John wrote:……It shows the foreshore at West Angle Bay, Pembrokeshire, Wales. The view looks westwards towards Milford Haven and shows the Lower Carboniferous Limestone contorted by a series of Variscan thrust related folds. One of the thrust planes is seen in the left of the image, over-steepened by the folding. To the centre of the image are a pair of whaleback periclinal anticlines. The beds then steepen again to vertical on the right via a tight syncline. But the beauty of a gigapan image is that one can dive in and view the detail like the slickenside lineations on the thrust plane or the writing on the buoy.

Long before I had a digital camera, I used a particular slide from a trip in the 1980s to introduce my students to the idea of the fascination of geology. It was taken next to one of the most famous photography spots in our national park system, but it is not a picture of the iconic feature. It’s the trail leading to it. Delicate Arch of the “Real” Jurassic Park lies just around the corner, and a crowd is often found there, especially at sunset. But I see fewer people stop and consider this scene….

I got into geology in part because of the wonderful journey of imagination that it is; a geologist is a world traveler, and a time traveler. The trail in this picture is formed on a natural break in the rock. Why is the break there?

In Jurassic time 180 and 140 million years ago, tidal flats and coastal sand dunes spread across this part of Utah. The surfaces of the dunes were pathways for all kinds of creatures, from insects to giant lumbering dinosaurs. The walked and crawled on these sands, and later the surfaces were preserved by subsequent layers of windblown sand. The surface later hardened a bit more than the others, and millions of years later, erosion exposed the old sands. A fracture developed along the surface, and the trail-builders of a few decades ago found it a great deal easier to just remove the overlying rock than to carve a new flat surface at great expense. And so it is that during our brief sojourn on the planet, we walk on the same surface, and perceive the significance of that fact. We use our minds to explore strange alien worlds, and yet these are the worlds that existed before ours and which became the raw materials for our own.Again, practically everyone walks up to Delicate Arch, but there is another arch just a few steps off the trail that provides a stunning view the distant La Sal Mountains, the laccolithic cores of 25 million year old volcanoes. This picture, taken just a few yards from the one above, contains the four elements of ancient human thought: water, earth, fire and sky (the water is in the sky and in the creek below). The essence of earth science…

This one is from New Zealand. The Nile River Caves (as featured in WOGE #263) are on the north-west side of South Island, New Zealand, and as well as the expected beautiful limestone features, have some wonderful glow-worms and some rather interesting strata.

This one in particular is a mixture of mudstone and limestone. By the time this layer emerges at the coast at Punukaki, it’s more clearly layered and makes the Pancake Rocks.

Yes, I have amazing glacier and volcano shots. But this one is the one that says “Geology” to me the loudest.

For my PhD research, I ended up working in the Swiss Alps. Day one out was long, long, long (and it was magically also my birthday). By the time we reached the col that was going to actually become my field area it was rather late in the day and we were still 1000 m above the closest road. Bridget (my field assistant) and I were wearing every item of clothing that we had in our packs due to the cold (there was still snow on the ground & it was July). Before we could call it a day, we decided to collect four samples (we had a number of other rocks from earlier at other sites to the south of the col). Three popped out without an issue in reasonable sizes (enough for thin sections, tomography, and bulk chemistry), but the fourth was stubborn. It came off in a huge sheet:

the large slab (behind the hammer) that eventually became 04AD15; Tom Foster in blue, Hannes Hunziker in the middle, and Lukas Baumgartner in pink

while Bridge and I proceeded to shiver, these three male geologists tried to get 04AD15 down to a reasonable size. They used the sledge. They used a hammer with a chisel. They hopped up & down on the slab. They wedged another rock underneath the slab and tried everything again. Eventually, pieces started to fall of the edges. In the end, 04AD15 is still my largest sample. But its also my best sample of the bunch (including what I got a year later!), so all that work was worth it. But whenever I look at anything related to the sample, I have to imagine three senior geologists trying like crazy to break the slab

Accretionary Wedge # 32

The March edition of the Accretionary Wedge geoblog carnival is at Ann’s Musings, and the theme is a deceptively simple summons: “Throw me your ‘favorite geologic picture’ mister.” This is nigh-on impossible and has led to some considerable introspection, not to mention scrabbling around to see what candidates I have with me on my laptop. But the scrabbling stopped as soon as I reminded myself of the image above. At first glance, perhaps it’s not strictly geological – but then again, yes it is. And, because of the very personal impact, it’s one of my favourite pictures – ever. It’s from a location in the remote south-western corner of Egypt, a Louvre of rock-art. This is just a small exhibit in a cave shelter covered in human expressions. The setting is geological, the canvas is geological, and the materials are geological, and all combine in the message of the connection between humans and geology. But of course it’s even more than that – we have no idea really who the artists were, exactly when they lived, what the function of this place was in their society, or why they expressed themselves so exuberantly. But the emotional resonance, sitting there gazing at this, has become deeply ingrained; there is an immediate, intensely human, connection with two unknown people who chose to record their hands reaching out to each other.It’s not even a picture of sand – but it is probably my favourite geological photo. And, in today’s world, perhaps it has an important message.

In a first moment I couldn’t decide what image to take, the classic outcrop or the marvellous landscape? – but there is an elder picture of 2007 I really like, at a first glimpse it’s geological context is not obvious, but this is also a reason that I like this particular picture.

The photo shows a species of club moss emerging from a pile of rubble. The club moss Huperzia selago is one of the two species of this genus present in the Alps; this species in particular can be found in high altitude and in glacier forelands, acting as pioneer species.
This specimen was emerging from gneiss and schist debris covering an active rock glacier; I like the contrast of the green plant to the cold grey of the rocks forming a sort of picture frame, the impression that the club moss overcomes every obstacle, even “breaks” the rocks apart to emerge from the underground.
For plants creeping debris and permafrost represent an ulterior challenge for colonization and growth in an already nasty environment, with long snow cover, low temperatures and deadly UV-radiation. I think the picture depicts well the struggle of existence in a harsh environment – but as the the rocks act as obstacle they at the same time also provide shelter, moisture and nutrients.

For the geologist also the recognition of even the smallest clue can be helpful, I find it fascinating how many different methods can be adopted to understand the development of a geomorphologic feature or a landscape – in combination with classic geological methods for example the vegetation cover or diversity can give indications of the recent activity of rock glaciers, or help to reconstruct the temporal development when other indicators are absent.

And finally the image remembers me as a sort of metaphor what the German geoscientist Gerd Lüttig argued in 1971:

“Earth history can be described as a permanent interaction between the geosphere (lithos) and life processes (bios). To investigate these processes is the mission of Lithobiontics, a new research discipline between Geology and Biology.“

In a post about Multnomah Falls and Columnar Jointing, I posted this picture taken of Sam at Devil’s Tower a few years ago. It remains one of my favorite pictures of geology (and Sam) as it provides such a great image to show several geologic principles at ones. Aside from the geologic signficance of the tower itself, the promionant geologic feature is the massive hexagonal piece that 7-year old Sam (for scale) is leaning against. Behind it, you can see the joints extending up the tower with clear hexagonal blocking roofs, allowing one to recognize the block as having weathered and fallen off the tower.

The picture also has trees and shrubs growing in the fractures below the main part of the tower. These fractures are not the columnar jointing of above, and so demonstrate a different condition of cooling for the base of the tower. The fractures below also have trees and shrubs growing amids the fractures illustrating yet another form of mechanical weathering.

This was taken from the appropriately named “Anticline Overlook” of the Canyon Rims Recreation Area in eastern Utah. The anticline is obvious, you can see the upward curve of the rock units. I love the part where the river cuts through the anticline making a natural road cut.

The river cuts through the Permian age Cutler formation, the left overs from the formation of the Ancestral Rockies. The upward arching of these rocks is from the squishing (a very technical term) of a buried salt layer. Far below the Cutler lies the Pennsylvanian Paradox formation, a mile thick layer of salt that has a tendency to move about creating some fun landscapes in the desert southwest. The buildings and ponds you see in the picture are a potash mine. Water is pumped underground into the Paradox layer, dissolves the salts and the brine is pumped back to the surface into the blue evaporation ponds in the background. The water evaporates away leaving the salts for transport.

The fun part of this area are the roads. They are barely visible in the picture but they travel hundreds of miles through the red rock desert . A mountain biking heaven!

I think this image is a perfect fit for Accretionary Wedge#32 “favorite geologic picture.” It’s not the most colorful or dramatic image, but it holds an important place in my professional experience in the geosciences.Arachnoids are geological features on Venus. They are characterized by a combination of radar-bright, concentric rings (like a bull’s eye) and radiating lineations (line-like features) and were named “arachnoids” because of their spider and web-like appearance.Although these features had been identified on earlier Soviet Venera mission data, the NASA Magellan mission provided sufficiently high resolution radar imagery and elevation data to investigate them more closely.These features were one of my first forays into geology research as an undergraduate student. What were they? Did all features catalogued as arachnoids based on the radar images have similar topographic features? What caused them? Where they all the same age? Where were they located? Was there a terrestrial geology analog? I had many questions, a patient research advisor, and a short summer.The personal outcome was clear, though: I was hooked. Geology was fascinating, no matter where in the solar system. There were so many questions, and we didn’t have all the answers! This was a far cry from the textbook science of packaged information and rote facts to memorize. The science was alive, the questions infinite, and the data plentiful.Whenever I see these data images, they represent all of this in one snapshot: the excitement and mystery of geology.
He has more but you just have to go to his blog to read the rest of it.

And finally here’s the Captains float –
The Red River at sunrise, seen from a balloon about 1000 feet up in the air.

The Red River

The beads are thrown and are now on the wire connecting to the internet web. I hope you had a good time.

Now all good things must come to an end. The parade is over and it is time to go home. Thank you one and all for submitting something for this Accretionary Wedge – 32.
If you had something and didn’t get it in or if I missed it please leave a comment and I will add it later.

Post script:
Here’s a little bit about Mardi Gras for those who don’t celebrate it like we do in Louisiana.

For those of you who don’t know its officially Carnival time or Mardi Gras season (Twelfth night to Fat Tuesday i.e. Jan 6 to March 8 this year). Twelfth night is also know as the feast of the Epiphany and is celebrated by Christians as the day the three wise men came to visit the baby Jesus and is 12 days after Christmas. Fat Tuesday is the day before Ash Wednesday. Ash Wednesday is the first day of lent, a time where you are suppose to make sacrifices and give up things, in preparation of Easter which is 40 days later. Because people may give up drinking, certain foods etc for the forty days during lent they like to have a big blow out where they consume the food that they will be giving up. They usually do this the day before and thus the reason it is called Fat Tuesday or as the French call it Mardi Gras.

To celebrate together different groups of people with like interests get together and form Krewes. Most Krewes have a theme by which they go by. For example, in my area of LA there is a Krewe of doctors call Aesculapius and another one for Lawyers called Justinian and one of cat and dog lovers called Barcus and Meow. I am a member of the Krewe: Les Femmes Mystique. If you haven’t guessed it – its a group of women who are concerned about the community. Although we enjoy our parties we also like to give something back to the community. Every month we have a project to work on. This keeps the Krewe together during the year when the parties are not going on. Every month there is a different project, such as working at the food bank, help run the Susan G Coleman race for cancer, the march of dimes walk, gathering school supplies for children, getting and wrapping toys for the Toy’s for Tots program, etc. It varies from year to year what all we do.
But the thing that most people know the Krewes by are by their parades. My Krewe is not big enough to have a parade of their own so we augment other parades in the area by joining in on other floats in the parades. When you are on a float, you provide all of your own throws – the things you toss to people. People love to come and watch these parades because of the gaudy decorations and the stuff that gets tossed to them. Beads are the most common thing, but there are also other things tossed to like stuff animals, wrapped candies/food, plastic cups and fake coins called doubloons (which can become a collectors item). It’s whatever you want to buy and spend, but you are restricted to things that can’t hurt if tossed, also it can’t be offensive to the public in general.
If you ever go to a Mardi Gras parade there are certain things you should know. Namely they can’t throw anything if the float is not moving, so don’t try to stop a float to get something from it. Also if it lands on the ground put your foot on it and then after the float has gone by then reach down and pick it up. If you try to reach down and grab it expect someone to stomp on your hand. Also when the float goes by everyone says ‘Throw me something Mister’. The reason they do that is because the people on the floats are usually in costumes, with their faces covered. They cover their faces so they can remain anonymous.

Elaborate costumes are common with the Carnival. Most Krewes have a King, and a Queen and a Captain the rest of the float leaders are called Dukes and Duchess. Because they are royalty they like to dress up to the part, thus the elaborate costumes. These people hold their offices for one year, and then switch off at coronation Bals. There is also another bal that is thrown during the Carnival time where the other royalties come together to enjoy the hospitably of the different Krewes. The Captain of the Krewe organizes the bals and parade and is the person who is in contact with the other Krewes. The King and Queen are the official representatives of the Krewe for that year and are expected to attend most events. The King and Queen are very rarely married to each other. The spouse or significant other of the Royalty person is officially named their consort.

Mardi Gras is all about having fun and celebrating life. It is also about giving back to the community in which they live as a ways for friends and neighbors to get together so they can get to know each other better. For more about Mardi Gras here Wikipedia Mardi Gras.

Post Script:
I do want to thank everyone. I did have some technical difficulties with this but eventually figured things out. I do want to thank Callan for helpful suggestions, while I tried to get it done. I must admit I agreed to be a host more for my own benefit than yours. I’ve very inept with computers and doing things like this teaches me so much. I also do it so I can see all the amazing things that have developed in the geology field since I was last active in it. I enjoyed putting this blog together and it wouldn’t have been possible if it wasn’t for all the contributions I got. Again THANK YOU.